The present invention relates to a probe card and a method of forming the same.
The probe card has been used to electrically connect a tester to pads in a wafer chip for testing of a semiconductor device. A tungsten pin probe has been proposed and this probe has a structure as illustrated in FIG. 1. A plurality of tungsten pins 31 in the range of 50 .mu.m.phi. to 100 .mu.m.phi. are supported at their base portions by a supporter 32 whilst top portions of the tungsten pins 31 are held by a holder 33 so that the tops of the tungsten pins 31 are aligned to correspond to electrodes of a semiconductor device to be tested. The tops of the tungsten pins 31 contact the electrodes of the semiconductor device for characteristic test of the semiconductor device. As illustrated in FIG. 1, the tungsten pins 31 are narrowed in pitch toward the top portions thereof so that the pitch of the tungsten pins 31 at the top portions thereof is in the range of 0.5 mm to 5 mm, for which reason tungsten pins 31 cannot be used with the narrower electrode pitch of the semiconductor device for example in the scale of 100 micrometers. This tungsten pins 31 have a length in the range of 3 cm to 10 cm, for which reason high frequency performances over 100 MHz are deteriorated. Such probe is disclosed in the Japanese laid-open patent publication No. 6-118100.
In recent years, in place of the above probe, another probe has been proposed, which is a membrane probe as illustrated in FIG. 2. A plurality of probe interconnections 42 are formed on a surface of a film 41. The probe interconnections 42 are made of a conductive material such as copper whilst the film 41 is made of an insulative material such as polyimide. At the ends of the probe interconnections 42, bumps 43 are formed by a solder or a plating. Another surface of the film 41 is adhered via an elastomer 45 to a supporter 44. In this structure, it is possible to provide bumps on the surface of the film 41 to make electrical contact through the bumps to electrodes of the semiconductor device.
The conventional membrane probe has the following problems. If the plural bumps 43 and the electrodes of the semiconductor device do not have sufficiently high coplanarities, it seems that some bumps do not contact the electrodes of the semiconductor device. In order to prevent this problem, it is effective to provide flexibility to the interconnections to allow all the interconnections to contact the electrodes of the semiconductor device. This flexibility is provided only by the elastomer 45 formed on the other surface of the film 41, for which reason the amount of the deformation of the interconnections 42 are limited whereby the flexibility thereof is not responsive to the bowing of the semiconductor wafer.
Further, the probe interconnections 42 extend to a peripheral portion of the film 41 for connecting to an external device, for which purpose the probe interconnections have to have a sufficiently long length. This makes it difficult to achieve a substantial scale down of the probe. As a result, the probing is difficult for the semiconductor device having been formed over the wafer before a dicing process. The high frequency performance thereof is likely to be deteriorated.
In the above circumstances, it had been required to develop a novel probe card with improved reliability of contact to electrodes of the semiconductor device and that contacts a semiconductor device formed on a wafer, which is also improved in high frequency performance.